As disclosed in patent literature 1 as an example, a conventionally used capacitive acceleration sensor includes a substrate, a support portion formed on the substrate, a movable electrode supported by the support portion and is floated above the substrate, and a fixed electrode formed on the substrate. The above-described support portion, movable electrode, and fixed electrode (hereafter, collectively referred to as a sensing portion) are formed on one side of the substrate. The one side is parallel to a reference plane defined by an X-direction and a Y-direction.
The capacitive acceleration sensor disclosed in Patent Literature 1 is axisymmetric with respect to both a first direction passing through a center of the sensor and extending along the X-direction and a second direction passing through the center of the sensor and extending along the Y-direction. With this configuration, when a thermal distortion is produced in the substrate due to a temperature change, the thermal distortion is expected to be distributed symmetric with respect to each of the first direction and the second direction. Thus, thermal stress caused by the thermal distortion is suppressed from being anisotropically applied to the sensing portion. Accordingly, degradation in detection accuracy of the acceleration, which is caused by above-described thermal stress, is suppressed.
However, in the capacitive acceleration sensor, when multiple sensing portions are formed on one substrate, each of the sensing portions is not axisymmetric with respect to both the first direction and the second direction. For example, the capacitive acceleration sensor may be configured so that a sensing portion axisymmetric with respect to the first direction and asymmetric with respect to the second direction and a sensing portion asymmetric with respect to the first direction and axisymmetric with respect to the second direction are formed on one substrate. In this case, when the thermal distortion is produced in the substrate due to the temperature change, the distortion is asymmetric with respect to each of the first direction and the second direction. As a result, thermal stress caused by the distortion is anisotropically applied to each sensing portion and an acceleration detection accuracy of each sensing portion may be degraded. Further, the acceleration detection accuracy of each sensing portion may differ from one another.